doc: drop mentions to .pow files ($deity REST their soul)

Co-authored-by: Roberto Abdelkader Martínez Pérez <robertomartinezp@gmail.com>

examples/basic/02_FixLogGrep/FixLogGrep

@@ -0,0 +1,5 @@
+#!/usr/bin/env sh
+
+kapow route add /apache-errors - <<-'EOF'
+	cat /var/log/apache2/access.log | grep 'File does not exist' | kapow set /response/body
+EOF